Detailed explanation of python closures

I believe the word "closure" is familiar to most students who have studied programming, but sometimes it is still difficult to understand. Let’s look at the definition first:

A closure is an entity composed of a function and its associated reference environment. For example, there is such a definition in the reference resources: When implementing deep constraints, you need to create something that can explicitly represent the reference environment and bundle it with the relevant subroutines, so that the whole bundle is called closure.

Python closure (closure) is actually not a very complicated thing.

In layman’s terms: if in an internal function, a variable in the external scope (but not the global scope) is referenced, then the internal function is considered a closure. It is nothing more than an "inner" function, referred to by a name (variable), and this name (variable) is a local variable to the "outer" function that contains it.

Maybe you still don’t understand what a closure is after reading this. It doesn’t matter. You will definitely understand after reading the following small example!

#! /usr/bin/env python
# coding=utf-8
# http://www.pythontab.com

#Define a function
def plus(number):

#Define it inside the function A function, in fact, the function inside this is considered a closure
def plus_in(number_in):
#Print the number_in variable here so that everyone can know more clearly which variable is passed in
print str(number_in) + "rn "

         return number+number_in
#In fact, what is returned here is the result of the closure
      return plus_in


#Assign a value to the plus function, this 20 is the parameter number
v1=plus(20)

print v1(100) #Note that the 100 here actually gives the parameter number_in


The operation result:

100

120

Note: 100 is the result printed by print str(number_in) + "rn"